The present invention relates to rigging tables, and to methods and systems for assembling trusses using a rigging table.
Various processes and techniques have been used to manually fabricate steel open-web trusses. Such fabrication techniques may involve processes including cut-out, rigging, welding, inspection, and painting operations. The welding operation can be the bottleneck or rate-limiting operation limiting production capacity. In a cut-out operation, steel angle and rod chord and web components are cut to length with hydraulic shears, cut-off dies, hydraulic presses, or other cutting devices. The cut-out operation may further include shaping the end of the web components to form a desired shape and size. In a rigging operation, assembly workers, or riggers, arrange the sized components in proper position and clamp and tack-weld the components in place. In a welding operation, a team of welders apply structural welds at component connections to give the truss strength. In an inspection operation, an inspector verifies material sizes, component lengths, welds, and positions. In a painting operation, a truss is dipped in a tank of coating material, such as a water-based primer, drained of excess primer, dried, and then loaded onto a transport out of the plant.
An assembly table or rigging table may be used, which includes fixtures for positioning the chord and web components in position while the components are clamped and tack-welded together. The long (e.g., up to 65 feet) structural components at the top and bottom of the trusses are known as chords. Chords may be supplied from a position behind the riggers on either side of the rigging table. In the past, the riggers had to turn away from the table, work together to lift a chord overhead, turn back toward the table while holding the chord, and lower the chord into the appropriate fixtures on the table. Once the riggers added the shorter web components, or webs, to the chord portion on the table, a second chord portion may be added. The components were then clamped and tack welded together. In the past, the riggers typically used hand clamps for this purpose. The riggers then send the rigged truss to the welding area on transfer rollers.
Manual lifting of the chords can be inefficient. When lifting heavy chords overhead, the riggers take time and precautions to handle the chords safely. Manual hand clamping of truss components is also inefficient, requiring hand strength and operator judgment as to placement.
What has been needed is a rigging table that automates assembly of trusses of different sizes and allows easy adjustability.
A rigging table is presently disclosed for assembling trusses comprising:                a) a base having a generally longitudinal axis and a generally lateral extent;        b) at least two bunk assemblies movable along the base in at least the generally longitudinal axis, each bunk assembly capable of being positioned on the base relative to another bunk assembly;        c) each bunk assembly comprising:                    a frame extending along the lateral extent of the base; a pair of guides slidably positioned on the frame to move generally transverse to the longitudinal axis of the base toward and away from each other and able to be fastened in position on the frame to accommodate assembly of different sized trusses; and            a pair of automated clamp members each positioned relative to and moveable with one of the guides on the frame to accommodate assembly of different sized trusses, each clamp member capable of securing an intersection of a chord and one or more webs to facilitate assembly of a truss.                        
The guides may be capable of being indexed along the frame in predetermined increments adapted to assembly of different sized trusses and fastened to the frame to facilitate assembly of a truss. As an alternate, each guide may be capable of alternatively being slidable along the frame and fastened in position to facilitate assembly of different size trusses, or being indexed along the frame in predetermined increments adapted to assembly of different sized trusses and fastened to the frame to facilitate assembly of a truss.
Each bunk assembly may have clamp members each comprising:                a stop portion capable of positioning a chord and one or more webs during assembly of a truss; and        a clamp arm having an operative position capable of securing the chords and one or more webs in relation to the stop portion for assembly of the truss, and retracting after the truss is assembled.        
Each clamp member may further comprise an actuator capable of moving the clamp arm to secure the chord and one or more webs during assembly of a truss and retracting the clamp arm after the truss is assembled. Each actuator may include a mechanism selected from the group consisting of a servo mechanism, a hydraulic mechanism, and a pneumatic mechanism, and is capable of driving the clamp arm between the securing and retracting positions. Each actuator may, for example, include two actuating cylinders capable of being extended and retracted, and a chain connected between the two actuating cylinders about a sprocket such that the clamp arm is driven by the sprocket to move between the securing and retracting positions. Alternatively, each actuator may include a rack and pinion capable of driving the clamp arm between securing and retracting positions.
Each stop portion may include a nesting portion capable of positioning a chord portion of a truss during assembly. The nesting portion of each stop portion may be formed by an inner block and an outer block enabling the chord portion to be positioned there between.
The rigging table may further include at least one release member capable of disengaging an assembled truss from the clamp members. A release member may be attached to each frame of each bunk assembly.
A bunk assembly may include rollers capable of allowing assembled trusses to move generally longitudinally along the base, and at least one tilt arm capable of moving an assembled truss onto the rollers. Each roller may be attached to each frame of each bunk assembly.
The base of the rigging table may include rails extending along the generally longitudinal axis and are capable of supporting at least two bunk assemblies on a plurality of guide wheels, for example, attached to the frames of the bunk assemblies. The base rails are capable of allowing the bunk assemblies to move on the rails and be positioned to accommodate assembly of different size trusses.
The base of the rigging table may also include stops adjacent each lateral extent of the base, capable of selectively engaging at least a portion of the frame such that when the frame is positioned relative to the stops adjacent one lateral extent, a zero camber is provided in the assembled truss, and when the frame is positioned relative the stops adjacent the opposite lateral extent, a standard camber is provided in the assembled truss.
The rigging table may also include conveyors capable of moving chord portions, selected for a given truss to be assembled, into position under the bunk assemblies adjacent the lateral extent of the frames thereof. The rigging table may further include automated arms operative to engage a chord portion positioned under the bunk assemblies and move the chord portion to enable positioning the chord portion relative to the frame and guides for assembly of a truss. The rigging table may include an automated worker guard panel that is capable of moving to enable the chord portion to be moved from beneath the bunk assemblies to above the bunk assemblies for positioning for assembly of a truss, and moving back to facilitate movement of workers adjacent the lateral extent of the base.
A bunk assembly is disclosed for a rigging table comprising:                a) a frame extending along a longitudinal extent and a lateral extent;        b) a pair of guides slidably positioned on the frame to move generally along the lateral extent toward and away from each other and able to be fastened in position on the frame to accommodate assembly of different size trusses; and        c) a pair of automated clamp members each positioned relative to and moveable with one of the guides on the frame to accommodate assembly of different sized trusses, each clamp member capable of securing an intersection of a chord and one or more webs to facilitate assembly of a truss.        
The guides may be capable of being indexed along the frame in predetermined increments adapted to assembly of different sized trusses and fastened to the frame to facilitate assembly of a truss. Alternately, each guide of the bunk assembly may be capable of alternately being slidable along the frame and fastened in position to facilitate assembly of different size trusses, or being indexed along the frame in predetermined increments adapted to assembly of different sized trusses and fastened to the frame to facilitate assembly of a truss.
Each clamp member of the bunk assembly may include a stop portion capable of positioning a chord and one or more webs during assembly of a truss, and a clamp arm having an operative position capable of securing a chord and one or more webs in relation to the stop portion for assembly of the truss, and retracting after the truss is assembled. Each clamp member may include an actuator capable of moving the clamp arm to secure the components during assembly of a truss and retracting the clamp arm after the truss is assembled.
Each actuator may include a mechanism selected from the group consisting of a servo mechanism, a hydraulic mechanism, and a pneumatic mechanism, capable of driving the clamp arm between the securing and retracting positions. Each actuator may include, for example, two actuating cylinders capable of being extended and retracted, and a chain connected between the two actuating cylinders about a sprocket such that the clamp arm is driven by the sprocket to move between the securing and retracting positions. Alternatively, each actuator may include a rack and pinion capable of driving the clamp arm between the securing and retracting positions.
Each stop portion may include a nesting portion capable of positioning a chord portion of a truss during assembly. The nesting portion of each stop portion may be formed by an inner block and an outer block enabling a chord portion to be positioned there between.
The bunk assembly may include at least one release member capable of disengaging an assembled truss from the clamp members. The release member may be attached to the frame of the bunk assembly.
The bunk assembly may further include rollers capable of allowing assembled trusses to move generally longitudinally along a base of the rigging table, and at least one tilt arm capable of moving an assembled truss onto the rollers. At least one roller may be attached to the frame of the bunk assembly. The bunk assembly may include a plurality of guide wheels attached to the frame and capable of allowing the bunk assembly to move on rails and be positioned to accommodate assembly of different sized trusses.
The bunk assembly may further include stops for the guides, on each lateral extent of the bunk assembly, such that when the guides are positioned relative to the stops from one side, a zero camber is provided in the assembled truss, and when the guides are positioned relative to the stops at the opposite side, a standard camber is provided in the assembled truss.
A method is disclosed of assembling truss elements on a rigging table comprising:                a) assembling at least two bunk assemblies for a rigging table with each bunk assembly comprising a frame extending along a lateral extent and a longitudinal extent, a pair of guides slidably positioned on the frame to move generally along the lateral extent toward and away from each other and able to be fastened in position on the frame to accommodate assembly of different sized trusses, and a pair of automated clamp members each positioned relative to an moveable with one of the guides on the frame to accommodate assembly of different sized trusses, each clamp member capable of securing an intersection of a chord and one or more webs to facilitate assembly of a truss;        b) positioning each bunk assembly along the rigging table in desired relation to another bunk assembly to assemble trusses of a desired size;        c) positioning clamp members along the guides on each bunk assembly in desired relation to the other clamp members to assemble trusses of the desired size; and        d) positioning chords and webs of a truss and actuating the clamp members to hold the chords and webs is desired location to assemble a truss of the desired size.        
The method may further include securing chords and webs of a truss using a clamp arm in relation to a stop portion during assembly of a truss, and at least tack-welding the chords and webs together to assemble a truss. The method may further include the further step of lifting the tack-welded truss upward above the bunk assemblies.
These and other advantages and novel features, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings. Further disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, from a description of embodiments of the systems and methods as set forth in the remainder of the present application with reference to the drawings.